1. Field of the Invention
The present invention concerns a component for connecting a plurality of optical fibers to a multicore optical fiber and a method of making a component of this kind.
2. Description of the Prior Art
Multicore optical fibers are optical waveguides comprising a plurality of parallel waveguide cores in a common linear matrix.
The recent French patent application No 93/01674 proposes an optical waveguide having a plurality of cores in a common matrix, each core surrounded by optical cladding. The axes of the cores are disposed in the matrix so that the geometrical relationships between them are extremely precise, the respective positions of the axes of the cores being defined to within a few tenths of a micrometer.
FIG. 1 shows one example of an optical fiber F of this type. This fiber F comprises, in a matrix M, four optical waveguides G.sub.1 through G.sub.4 whose axes X.sub.1 through X.sub.4 form, in transverse section, the corners of an extremely precise square C.sub.1. The contours of the matrix M are defined by four identical portions R.sub.1 through R.sub.4 of cylinders of revolution, the axes of which respectively coincide with the axes X.sub.1 through X.sub.4 of the optical waveguides.
This multicore fiber F has a maximal outside diameter D equal to 125 .mu.m, for example, the width d of the square C.sub.1 being 44.19 .mu.m, the radius r of the cylindrical arcs R.sub.1 through R.sub.4 being equal to 31.25 .mu.m.
Reserved until now primarily for long-haul transmission and trunk networks, fiber optics will be increasingly used in distribution networks with terminations in distribution chambers, in business premises and eventually in the home. As the number of customers connected by optical fiber increases, the overall economic aspect of the network becomes of capital importance.
Two types of architecture are feasible:
a shared type of architecture in which, using multiplexers, couplers and splitters, a single downward channel is used for many users, the transmission cost and the costs of the components and the fiber being divided by the number of users served by this single fiber; PA1 an architecture using multicore fibers, with n waveguides connecting n users, which saves the cost of the multiplexers, couplers and splitters, which are all relatively costly components. PA1 a plurality of fibres are assembled so that optical claddings of said fibers are tangential to each other and so that axes of their cores are disposed in a geometry corresponding to that of a multicore fiber to which said component is to be connected, and PA1 said fibers assembled together in this way are fixed to a support having at least one reference surface. PA1 said fibers are inserted into a U-section groove at least part of which is formed in an elastomer material part and closed by a reference support, the section of said groove being such that said optical claddings of said fibers, to which pressure is applied by virtue of the elasticity of said part, are located tangentially to each other and with their cores disposed in said geometry, PA1 said fibers are fixed to said support, PA1 said fibers and said support are removed from said groove. PA1 a multicore fiber to be connected to said connection component is inserted into said groove at the same time as said fibers so that it is aligned with said fibers in said groove which has a shape such that said multicore fiber is positioned in it with the axes of its cores coincident with the axes of the cores of said fibers, and PA1 said fibers and said multicore fiber are fixed to said support. PA1 a one-piece block having a convex groove in a longitudinal plane of symmetry of said block is machined flat perpendicularly to said longitudinal plane of symmetry and to a transverse plane of symmetry of said block so as to obtain in said transverse plane of symmetry of said block a groove height equal to .sqroot.2d where d is the diameter of the optical claddings of said fibers to be assembled, said one-piece block having at least one reference surface parallel to its longitudinal plane of symmetry, PA1 said block is sawn apart in its transverse plane of symmetry, PA1 the two half-blocks thus obtained are placed together with the two reference half-surfaces in a common plane and with the sawn through ends of the two half-blocks coincident so that their grooves together define at said sawn ends a square cavity, PA1 said optical fibers are inserted into said square cavity and PA1 said two half-blocks and said fibers inserted therein are fixed together, the assembled two half-blocks defining a reference support for the assembled fibers. PA1 an end-piece with dihedral surfaces is placed in an end-piece receiving groove of a precision transfer part of the type with dihedral grooves, PA1 said fibers to be assembled are inserted into said end-piece from one end thereof, exiting from the other end of said end-piece into a fiber receiving groove, PA1 said fiber receiving groove is closed by a punch having a complementary groove defining with said fiber receiving groove a generally square cavity, PA1 said fibers are positioned in said cavity using a binocular microscope, PA1 said fibers are fixed in said end-piece which provides a reference support.
The cabling, installation and civil engineering costs being preponderant in cost calculations at present, there is nevertheless a trend towards this second type of architecture, i.e. to networks of multicore fibers.
As yet, no component for connecting a multicore fiber to individual fibers has been proposed.
One object of the invention is to propose a component of this kind, and a method of making it.